Thank you Fiernaq for your feedback.
Since Squiggle is server-less its not possible to prevent people from impersonating someone else.
However Squiggle does show you the user's machine name on contact info tool tip so impersonation can be detected that way (That too can be faked if someone wants to do it).
To address this issue we would need a presence server which will have to be installed on a machine in the network but that will make deployment a bit difficult and Squiggle as server oriented messaging service.
If enough people request for this, I'll consider this.